What do you want to bet Rudy Giuliani thinks

[Silent3]

8. Well, I suppose...

(not that I'm giving Trump any credit for having the faintest clue of what he's talking about), if you're talking about deleting data stored on a hard drive you could use something caustic on the innards of a hard drive to breakdown the magnetic coating, and that could help defeat many data recovery techniques.

Emails specifically, however, even if you have your own email server, get relayed and bounced around between plenty of servers, so controlling just one server isn't enough to cover your email tracks except for the very limited case of email exchanged between accounts that are both hosted on the same server.